How to use blender create square-section spiral objects?
To make a spiral 

Press &#9096; Ctrl+&#9095; Alt+U to access the user preferences

And enable the extra objects add-on: 



Back in the 3d viewport, press &#8679; Shift+A and add a Curve>Curve Spirals>Archimedian

Set the steps, turns and radius grow to get a spiral that looks the way you want.



To give it shape, use another curve with the profile you want (I used a curve>circle and adjusted the handles to make the shape more square).

In object mode select the spiral and use that newly created curve as bevel object. Make sure you enable the fill cap option.